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Home >> Chevrolet >> 2008 >> Optra5 LS, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 2.0L (Diesel) >> Diagnostic Information and Procedures >> DTC P1691 >> Circuit/System Description

Circuit/System Description

The engine control module (ECM) controls the engine coolant temperature (ETC) gage by pulsing the control circuit to ground at a predetermined hertz rate. The ECM monitors the voltage on the engine coolant temperature (ECT) output circuit. If the ECM determines the voltage is out of the normal operating range or detects a high temperature condition, a DTC sets.